However, I came away from giving evidence to the London Assembly’s first-rate transport committee this week pretty sure that some of the people backing a third or even fourth runway at Heathrow don’t get it. It is simple: it will be politics – not economics, noise or climate change – that will determine where, if anywhere, new runways will be built. I don’t mean that the decision will necessarily be narrowly party political; simply that it will based on a political assessment of how deliverable any proposal for a new runway actually is.

“It will be politics – not economics, noise or climate change – that will determine where, if anywhere, new runways will be built”.

Steve Norris has consistently argued that a third runway at Heathrow is politically undeliverable. British Airways chief Willie Walsh has come to the same conclusion. He is now planning his business on the basis that a third runway will not be built. He is buying up Heathrow slots from other airlines and consolidating hisMadridbase through his link up with Iberian airlines.

I think they are right. The last Labour Government tried and failed to expand Heathrow. It lost out to a vibrant, rainbow coalition of local residents, local authorities, MPs and peers from across the political spectrum, trade unionists and business people as well as large sections of the environmental movement including direct action activists – http://www.hacan.org.uk/resources/reports/how.the.heathrow.campaign.was.won.pdf. That coalition is merely dormant. It would come back. It would come back more confident than before. It now knows how to defeat a runway. Moreover, it knows it has provided inspiration to campaigners across Europe – fromMunich toSiena – to see off their runway proposals. This is the political reality that would face any party that tried to expand Heathrow. Politicians are realists. Not one would want to risk losing another 10 year battle, achieved nothing in the process.

“The vibrant campaign which saw off expansion at Heathrow last time round is likely to frighten off politicians from backing a 3rd runway. That is the political reality.”

And then there are the voters. 725,000 of them live under the Heathrow flight paths, according to EU statistics (see table below). That, incredibly, is 28% of all people disturbed by aircraft noise right acrossEurope. That’s more people than live inGlasgoworManchester. A third runway, according to Department of Transport figures, would add at least another 150,000.

It is difficult to assess to what extent those organisations – think-tanks, businesses, trade unions – which back a third or fourth runway have thought through the political barriers to Heathrow expansion. I suspect they instinctively feel that the Coalition’s decision to scrap a third runway and mixed-mode (more planes on the existing runways) was a one-off, an aberration, something David Cameron repents of in private. George Osborne, they claim, is on their side. The tide, they feel, is turning in their favour. It is only a matter of time, they believe, before Sipson is flattened and normal service has been resumed.

That, I think, is to misunderstand the history of protest. I was involved in the campaigns against road building in London in the late 1980s and early 1990s; road building plans that would have flattened dozens of communities. The scale of the protests killed off major new roads as a solution to London’s traffic problems. Equally, the national ‘anti-roads’ protests in the 1990s changed the course of UK transport policy.

The anti-expansion campaign at Heathrow over the last decade or so is likely to be equally significant. It will frighten off any political party from supporting further expansion of the airport. Boris knows his former constituents in Henley would be up in arms. Maria Eagle, backed by her leader Ed Miliband, has made an astute political decision to oppose expansion. Heathrow Airport knows it has the fight of its life on its hands to get a new runway. That is the political reality. If George Osborne – or Ed Balls – doesn’t get it, they are in for a very noisy wake-up call.